Nuclear fusion is extraordinarily powerful:

“…we discovered that fusion powered the stars only about a hundred years ago, when the British physicist Arthur Eddington put together two pieces of knowledge into what was seen at the time as a wild surmise. The facts he combined were that the sun is made up mostly of hydrogen, with some helium, and that E=mc2.

“Eddington noticed that four hydrogen atoms weigh a tiny bit more than one helium atom. If four hydrogen nuclei somehow fuse together, in a series of steps, and form helium, then a little bit of mass must be “lost” in the process. And if one takes seriously that most famous of equations, then that little bit of mass becomes a lot of energy – as much energy as that amount of mass multiplied by the speed of light, squared. To give a sense of this ratio: If you converted a baseball into pure energy, you could power New York City for about two weeks. Maybe that process – hydrogen crashing into hydrogen and forming helium, giving off an extraordinary amount of energy in the process – was how the sun and all the stars burned so bright and so long. Eddington, in a paper laying out this theory, closed with an unusual take on the story of Daedalus and his son Icarus. Eddington argued in defense of Icarus, saying it was better to fly too high, and in doing so see where a scientific idea begins to fail, than it was to be cautious and not try to fly high at all.”

It’s also remarkably safe, and generates no problematic waste – unlike nuclear fission. But it’s always just around the corner, and has never really progressed towards commercial viability. But there are still scientists working on it, still progress is being made, and this New Yorker article looks at one particular team’s efforts to solve the (many) remaining problems.